Pharmacokinetics of repeated single oral doses of enalapril maleate (mk-421) in normal volunteers

Enalapril, the ethyl ester of a potent angiotensin converting enzyme inhibitor, enalaprilat, was administered to healthy volunteers as a capsule containing 10 mg of the maleate salt, every 24 h for eight doses. Serum profiles show little accumulation of enalaprilat following eight daily doses of enalapril maleate. An average effective half-life for accumulation of approximately 11 h was calculated from urine data. Comparison of observed 24-h urinary recoveries of enalaprilat to predicted steady-state recovery indicates that an ‘average’ steady state for enalaprilat is attained by the third or fourth dose of enalapril maleate. Statistical comparison of daily urinary recoveries, as well as C_min values for enalaprilat, confirm this. Observed fluctuations in serum and urine data during apparent steady state suggest some day-to-day variability in the absorption of enalapril maleate and/or its hydrolysis to enalaprilat. An accumulation ratio of 1·3 for enalaprilat was calculated from the predicted steady-state urinary recovery and observed urinary recovery for dose one.     

Use of microcalorimetry in determination of stability of enalapril maleate and enalapril maleate tablet formulations

The stability properties of enalapril maleate (EM) and of different tablet formulations including EM were studied by isothermal microcalorimetry and by high performance liquid chromatography (HPLC). It was shown that water content of the sample and elevated temperature have a high impact on stability properties of the substance itself and of the formulations including this substance. The degradation is more extensive at higher water content and at elevated temperature. The type of the tablet formulation (5 or 20mg EM tablet formulation) also has an impact: the 5 EM tablet formulation is the less stable one. The heat output of individual tablet formulations was used to evaluate the enthalpy changes and to calculate the difference in the amount of degraded EM between various samples. These results agreed satisfactorily with those obtained by HPLC. Isothermal microcalorimetry proved to be a fast and predictive method that could be used in preformulation studies to accelerate the pharmaceutical development and shorten the time before launching the product to the market.     

马来酸依那普利片治疗原发性高血压的疗效及安全性分析

目的探讨马来酸依那普利片治疗原发性高血压的疗效及安全性。方法 90例原发性高血压患者,按随机数字表法分成观察组和对照组。对照组给予卡托普利片治疗;观察组给予马来酸依那普利片治疗。结果观察组总有效率为95.56%,高于对照组的80.00%,差异有统计学意义(P<0.01)。观察组副反应总发生率为8.89%,少于对照组的24.44%,差异有统计学意义(P<0.05)。结论马来酸依那普利片治疗原发性高血压疗效可靠,具有良好的安全性。     

Bioequivalence study of two enalapril maleate tablet formulations in healthy male volunteers Pharmacokinetic versus pharmacodynamic approach

Objective: Two different conventional release enalapril maleate tablet formulations were evaluated for their relative bioavailability (Eupressin tablets 10 mg, Biosintética as the test formulation vs Renitec tablets 10 mg Merck Sharp & Dhome, as the reference formulation). A single 20 mg oral dose of each preparation was administered to 18 healthy male adult volunteers and their bioequivalence was assessed by comparing the serum enalaprilat and total enalapril (enalaprilat plus enalapril maleate) concentration-time curves. Angiotensin converting enzyme (ACE) activity was also quantified in each serum sample. Results: The pharmacokinetic parameters obtained for each formulation were the area under the time-concentration curve from 0 to 24 h (AUC_[0–24]), maximum concentration C_max and the time at which it occurred (t_max). When serum enalaprilat concentration-time curves were employed to assess bioequivalence, the formulations were bioequivalent in the extent but not in the rate of absorption. However, no difference in either the extent or the rate of absorption were observed when serum total enalapril vs time curves were analysed. ACE activity-time curves were similar for both formulations and showed that ACE was 90% inhibited 3–5 h after enalapril administration, and till approximately 50% after 24 h. At that time, circulating enalaprilat and total enalapril levels were less than the tenth of C_max. Conclusion: The results show that complete bioequivalence of the two formulations can be concluded from serum total enalapril concentration data, and that serum ACE activity is not a suitable pharmacodynamic variable for assessing bioequivalence. Received: 29 May 1995/Accepted in revised form: 30 October 1995     

Identification of new impurities of enalapril maleate on oxidation in the presence of magnesium monoperoxyphthalate

Stress stability testing and forced degradation were used to determine the stability of enalapril maleate (EM) and to find a degradation pathway for the drug. The degradation impurities, formed under different stressed conditions, were investigated by HPLC and UPLC–MS methods. HPLC analysis showed several degradation impurities of which several were already determined, but on oxidation in the presence of magnesium monoperoxyphthalate (MMPP) several impurities of EM were observed which were not yet characterized. The HPLC methods for determination of EM were validated. The linearity of HPLC method was established in the concentration range between 0.5 and 10 μg/mL with correlation coefficient greater than 0.99. The LOD of EM was 0.2 μg/mL and LOQ was 0.5 μg/mL. The validated HPLC method was used to determine the degradation impurities in samples after stress stability testing and forced degradation of EM. In order to identify new degradation impurities of EM after forced degradation UPLC–MS/MSⁿ, Orbitrap has been used. It was found that new impurities are oxidation products: (S)-1-((S)-2-((S)-1-ethoxy-4-(o,m,p-hydroxyphenyl)-1-oxobutan-2-ylamino)propanoyl)pyrrolidine-2-carboxylic acid, (2S)-1-((2S)-2-((2S)-1-ethoxy-4-hydroxy-1-oxo-4-phenylbutan-2-ylamino)propanoyl)pyrrolidine-2-carboxylic acid. (S)-2-(3-phenylpropylamino)-1-(pyrrolidin-1-yl)propan-1-one was identified as a new degradation impurity.     

马来酸依那普利与缬沙坦联合治疗糖尿病肾病的临床观察

目的：探讨马来酸依那普利与缬沙坦联合治疗糖尿病肾病的临床疗效。方法：将本院2010年2月～2011年5月收治的糖尿病肾病患者70例,随机分为对照组与治疗组,每组35例,对照组单独给予马来酸依那普利治疗,治疗组给予马来酸依那普利与缬沙坦联合治疗,两组均连续治疗24周。比较两组治疗前后的血压（SBP和DBP）和空腹血糖（FBG）;检测两组治疗前后的24h尿蛋白（24-Upr）、血肌酐（SCr）、尿素氮（BUN）、尿β2微球蛋白（β2-MG）值等肾功能指标。结果：治疗后,两组的血压和FBG比较差异无统计学意义（P〉0.05）;治疗后,治疗组的24-Upr、SCr、BUN以及β2-MG较对照组有显著下降（P〈0.05）。结论：马来酸依那普利联合缬沙坦对糖尿病肾病患者的肾功能具有良好的保护作用,值得推广应用。     

Improvement of enalapril maleate chemical stability by high shear melting granulation

Abstract

Enalapril maleate is a widely used drug, which is chemically unstable when mixed with excipients resulting in enalaprilat and diketopiperazine as the main degradation products. The preparation of enalapril sodium salt has been used to improve drug stability in solid dosage forms; however, product rejection is observed when the chemical reaction for obtaining the sodium salt is not completely finished before packaging. In this study, granules were prepared by melting granulation using stearic acid or glyceryl monostearate, with a view to developing more stable enalapril maleate solid dosage forms. The granules were prepared in a laboratory-scale high shear mixer and compressed in a rotary machine. Size distribution, flow properties, in vitro drug release and enalapril maleate chemical stability were evaluated and compared with data obtained from tablets prepared without hydrophobic binders. All formulations showed good physical properties and immediate drug release. The greatest improvement in the enalapril maleate stability was observed in formulations containing stearic acid. This study showed that hot melting granulation could be successfully used to prepare enalapril maleate granules which could substitute the in situ formation of enalapril sodium salt, since they provided better enalapril stability in solid dosage forms.     

Psychotropic effects of enalapril maleate in normal volunteers

In order to establish any psychotropic effects of the angiotensin-converting enzyme inhibitor enalapril, the drug was administered in doses of 20 mg every morning for 14 days to 12 normal subjects, and compared with placebo on a battery of physiological, psychological and subjective tests, before and after the dose on the 1st and 14th days.Diastolic blood pressure was significantly reduced and heart-rate increased by enalapril as compared with placebo; one component (P ₁-N ₁) of the auditory evoked EEG response was increased and tapping rate quickened. The commonest side effect was tiredness.It was concluded that enalapril (unlike most other antihypertensive agents) did not lower mood but could enhance attention and alertness.     

马来酸依那普利叶酸片对H型高血压患者内皮细胞损伤标志物及血清同型半胱氨酸水平的影响

目的：探讨马来酸依那普利叶酸片对 H 型高血压患者内皮细胞损伤标志物及血清同型半胱氨酸（Hcy）水平的影响。方法选取2013年2月—2014年2月贵阳市第二人民医院收治的 H 型高血压1级患者98例,随机分为试验组（52例）与对照组（46例）。试验组患者予以马来酸依那普利叶酸片治疗,对照组患者予以吲达帕胺片治疗。观察两组患者治疗前后内皮细胞损伤标志物〔P -选择素、血栓调节蛋白（TM）、血管性假血友病因子（vWF）〕及血清 Hcy 水平。结果治疗前两组患者 P -选择素、TM、vWF 及血清 Hcy 水平比较,差异无统计学意义（P ﹥0.05）;治疗后试验组患者 P -选择素、TM、vWF 及血清 Hcy 水平低于对照组,差异有统计学意义（P ﹤0.05）。结论马来酸依那普利叶酸片治疗 H 型高血压的效果显著,能降低内皮细胞损伤标志物及血清 Hcy 水平,改善受损的血管内皮细胞功能,有效防止心脑事件的发生。     

RP-HPLC法测定马来酸氯苯那敏片中马来酸氯苯那敏的含量

目的建立以反相高效液相色谱法测定马来酸氯苯那敏片中马来酸氯苯那敏含量的方法。方法色谱柱为Agilnet TC-C18（150mm×4.6mm,5μm）,流动相为0.005mol/L辛烷磺酸钠（用醋酸调节pH3.0）∶乙腈=3∶1,流速为1.0ml/min,柱温为30℃,检测波长为260nm。结果马来酸氯苯那敏浓度在0.005～0.05mg/ml范围内与峰面积积分值呈良好线性关系（r=0.9995）;平均回收率为99.0%,RSD=0.8%（n=9）。结论本方法操作简便,测定结果准确、重现性好,可用于测定马来酸氯苯那敏片中马来酸氯苯那敏的含量。     

Stability and in vitro release profile of enalapril maleate from different commercially available tablets: possible therapeutic implications

Stability of enalapril maleate formulations can be affected when the product is exposed to higher temperature and humidity, with the formation of two main degradation products: enalaprilat and a diketopiperazine derivative. In this work, stability and drug release profiles of 20 mg enalapril maleate tablets (reference, generic and similar products) were evaluated. After 180 days of the accelerated stability testing, most products did not exhibit the specified amount of drug. Additionally, drug release profiles were markedly different from that of the reference product, mainly due to drug degradation. Changes in drug concentration and drug release profile of enalapril formulations are strong indicators of a compromised bioavailability, with possible interferences on the therapeutic response for this drug.     

Stability of enalapril repackaged into monitored dosage system

A monitored dosage system (MDS) is a professionally prepared blister-type repackaging system used to improve medication adherence. The objective of this study was to determine the stability of enalapril tablets, a widely prescribed drug, commonly used by the elderly but potentially unstable in MDSs. No degradation of enalapril tablets repackaged into MDSs was observed during the 60 day study period.     

马来酸依那普利片稳定性研究

目的 提高马来酸依那普利片的稳定性。方法 将马来酸依那普利原料和碳酸氢钠以1:3的摩尔比溶解在水中,作为粘合剂使用。结果 通过原辅料相容性试验表明,处理后的API与各辅料相容性较好,杂质没有明显变化;通过制剂的加速6个月试验表明：杂质C由0.15%增长至0.61%,杂质D由未检出增长到0.48%;通过长期12个月的数据表明：杂质C由0.15%增长至0.42%,杂质D由未检出增长至0.1%。结论 通过原辅料相容性和稳定性考察结果显示,该工艺有效解决了马来酸依那普利制剂稳定性不好的问题。     

Multivariate data analysis as a tool to investigate the reaction kinetics of intramolecular cyclization of enalapril maleate studied by isothermal and non-isothermal FT-IR microscopy

In this paper, the use of multivariate data analysis approach to investigate the kinetics of solid-state reaction monitored via FT-IR thermal microscopy is discussed. The solid-state degradation of enalapril maleate was monitored non-isothermally at temperature range from 25 to 200 °C and isothermally at various temperatures (115, 120, 125, 130, and 135 °C) for a few hours. The collected FT-IR spectra were subjected to self-modeling curve resolution (SMCR) in order to elucidate the pure component spectral estimates. Subsequently, the relative contributions from the observed species could be obtained by projecting the pure component spectral estimates onto the collected FT-IR spectra. Accordingly, the conversion factors from enalapril maleate to diketopiperazine were calculated and were fitted to various solid-state reaction models. The activation energy values (E_a) calculated from seven nucleation models were ranging from 176.4 to 193.9 kJ/mol. This multivariate data analysis approach proves to be an effective tool for analyzing the kinetic spectroscopic data having a high degree of overlap between original compound and its degradation product since the information from the whole spectral range is used.     

Study of forced degradation behavior of enalapril maleate by LC and LC-MS and development of a validated stability-indicating assay method

In the present study, comprehensive stress testing of enalapril maleate was carried out according to ICH guideline Q1A(R2). The drug was subjected to acid (0.1N HCl), neutral and alkaline (0.1N NaOH) hydrolytic conditions at 80 degrees C, as well as to oxidative decomposition at room temperature. Photolysis was carried out in 0.1N HCl, water and 0.1N NaOH at 40 degrees C. Additionally, the solid drug was subjected to 50 degrees C for 60 days in a dri-bath, and to the combined effect of temperature and humidity, with and without light, at 40 degrees C/75% RH. The products formed under different stress conditions were investigated by LC and LC-MS. The LC method that could separate all degradation products formed under various stress conditions involved a C18 column and a mobile phase comprising of ACN and phosphate buffer (pH 3). The flow rate and detection wavelength were 1 ml min(-1) and 210 nm, respectively. The developed method was found to be precise, accurate, specific and selective. It was suitably modified for LC-MS studies by replacing phosphate buffer with water, where pH was adjusted to 3.0 with formic acid. The drug showed instability in solution state (under acidic, neutral, alkaline and photolytic stress conditions), but was relatively stable in the solid-state, except formation of minor products under accelerated conditions. Primarily, maximum degradation products were formed in acid conditions, though the same were also produced variably under other stress conditions. The LC-MS m/z values and fragmentation patterns of two of the five products matched with enalaprilat and diketopiperazine derivative, previously known degradation products of enalapril. Also, m/z value of another product matched with an impurity listed in the drug monograph in European Pharmacopoeia. Rest two were hitherto unknown degradation products. The products were characterized through LC-MS fragmentation studies. Based on the results, a more complete degradation pathway for the drug could be proposed.     

HPLC-QTOFMS法测定马来酸依那普利及中间体中的对甲苯磺酸乙酯

目的:建立HPLC-QTOF MS测定马来酸依那普利及中间体N-[1-(S)-乙氧甲酰基-3-苯丙基]-L-丙氨酸中对甲苯磺酸乙酯的方法。方法:采用Eclipse plus C18色谱柱(3.0 mm×100 mm,1.8μm),以20 mmol·L-1甲酸铵水溶液(A)-乙腈(B)为流动相,梯度洗脱(0～2 min,10%→50%B;2～4 min,50%→60%B;4～7 min,60%→90%B;7～8 min,90%B),流速1.0 mL·min-1,柱温50℃;采用正离子模式采集数据。结果:对甲苯磺酸乙酯浓度在0.20～5.01μg.mL-1范围内线性关系良好(r=0.9955);日内和日间精密度良好,RSD小于6.7%;定量限和检测限分别为0.4 ng、0.2 ng;马来酸依那普利及中间体回收率(n=9)分别为102.6%和90.8%。结论:本法简便、灵敏,可用于对甲苯磺酸乙酯的定量研究。     

络合萃取分光光度法测定鼻宝片中马来酸氯苯那敏的含量

用锌试剂络合,二氯乙烷萃取及分光光度法测定鼻宝片中马来酸氯苯那敏的含量。实验证明,马来酸氯苯那敏在2.5～20.0μg/ml范围内呈良好线性关系,r=0.9997,平均回收率为98.7%,RSD为1.51%(n=5)。该方法准确,可靠,达到质量控制的目的。     

马来酸依那普利片的药动学及相对生物利用度

目的研究马来酸依那普利片在健康人体内的药动学及相对生物利用度。方法用双周期交叉实验设计,采用液相色谱-质谱-质谱联用法测定18名健康男性受试者口服马来酸依那普利片(受试制剂)和悦宁定(参比制剂)后不同时刻血浆中依那普利和其活性代谢物依那普利拉的浓度,绘制血药浓度-时间曲线并计算主要药动学参数。结果18名受试者口服含马来酸依那普利20 mg的受试制剂和参比制剂后血浆中依那普利的tm ax分别为(0.83±0.44)和(0.93±0.37)h,ρm ax分别为(70.54±26.84)和(67.01±23.75)μg.L-1,t1/2分别为(2.13±0.52)和(2.14±0.42)h,AUC0t-分别为(122.82±45.31)和(121.45±43.06)μg.h.L-1,AUC0-∞分别为(123.77±45.36)和(122.55±43.32)μg.h.L-1;依那普利拉的tm ax分别为(3.72±1.18)和(3.61±0.92)h,ρm ax分别为(33.14±9.72)和(34.15±10.98)μg.L-1,t1/2分别为(8.88±1.35)和(8.99±1.09)h,AUC0-t分别为(301.64±82.71)和(316.47±99.09)μg.h.L-1,AUC0-∞分别为(307.32±83.54)和(322.70±100.67)μg.h.L-1,以AUC0-t计算,马来酸依那普利的平均相对生物利用度为(103.0±20.1)%,依那普利拉的平均相对生物利用度为(98.4±22.4)%。结论根据双单侧检验表明2种制剂具有生物等效性。     

HPLC法测定马来酸依那普利分散片的有关物质

摘 要 目的： 建立高效液相色谱法测定马来酸依那普利分散片的有关物质。方法: 采用Kromasil 100 SC₈色谱柱（250 mm×4.6 mm,5 μm）,以0.01 mol·L^-1磷酸二氢钾溶液（用磷酸调节pH为2.2）为流动相A,乙腈为流动相B梯度洗脱,流量1.0 ml· min^-1,检测波长215 nm,柱温40℃,进样量20 μl。结果: 依那普利拉、马来酸依那普利及依那普利双酮的浓度分别在14.64～43.92μg·mL^-1（r=0.999 8）;9.29～27.87 μg·mL^-1（r=0.999 1）;10.80～32.40 μg·mL^-1（r=0.999 5）范围内与峰面积呈良好的线性关系。采用《中国药典》方法测得依那普利拉未检出,依那普利双酮含量为0.2%,采用梯度洗脱方法测得依那普利拉、依那普利双酮含量分别为0.1%、0.2%, 主药与有关物质能达到较好的基线分离。结论:该方法灵敏度高,专属性强,准确可靠, 可用于该药品质量控制。     

HPLC法测定氯芬黄敏片中马来酸氯苯那敏和双氯芬酸钠含量

目的建立用HPLC法测定氯芬黄敏片中马来酸氯苯那敏和双氯芬酸钠含量的方法。方法使用C1 8硅烷键合硅胶柱(250 nm×4.6 mm),检测波长262 nm,用庚烷磺酸钠溶液-甲醇-乙腈(25∶30∶18)为流动相。结果马来酸氯苯那敏和双氯芬酸钠的线性范围分别为16.63~83.15 mg.L-1,r=0.9999;100.8~504.0 mg.L-1,r=0.9997(n=5)。方法的平均回收率分别为100.7%和98.8%(n=9)。结论该方法简便、准确、重复性好,可用于氯芬黄敏片中马来酸氯苯那敏和双氯芬酸钠含量的测定。